Do magnesium calmers really work?

An internet search or visit to your local feed store will lead to an array of calming supplements. Although magnesium based supplements have been a popular choice for many years, there is very little scientific evidence to support their use. Whilst initial research conducted in collaboration with SPILLERS produced some promising results, a follow-up study suggests that magnesium may not reliably modify behaviour after all.

Previous research

A small study published in 2015 found that feeding 10g of supplementary magnesium in the form of magnesium aspartate (a very available source of magnesium) could significantly reduce reaction speed. However it was unclear whether it was the magnesium or the aspartate, an amino acid (building block of protein) which acts as chemical messenger that was responsible.

What is reaction speed?

Horses are prey animals and evolved to take flight under times of stress – a trait that many horse owners feel only too aware of! However assessing behaviour can be subjective so in order to conduct a scientifically fair test, a method of reliably and consistently measuring the effect (if any) of feeding supplementary magnesium was required. In both studies, reaction speed was therefore measured as the time taken to travel a set distance after being startled using a previously approved protocol.

New research conducted in collaboration with SPILLERS

To test whether the results from the previous study could be repeated and if so, whether it was the magnesium or the aspartate that was responsible, 6 Thoroughbreds, 6 Arabs and 6 ponies were fed 3 different diets for 7 days in a random order:

10 Comments

My understanding is that where a horses diet is deficient in magnesium, this can cause the horse to be more on edge and sharp. It is therefore important to check the levels available in all feed and forage and to balance accordingly taking account of antagonists.

This evidence still not very convincing given small sample size of 18 horses and three different diets! Also what was the baseline behaviour of these horses like? Need larger numbers and behaviours (ensuring no health related cause for behaviour excluded)to conduct scientific trial. Not easy! but required to evaluate fully

I fed feed mark steady up supplement for a while to try and calm my thoroughbred. I wasn’t convinced it was doing any good! I moved yards took him off haglage and all he has is dengie healthy tummy complete feed and a consistent routine. He is a completely different horse less spooky and enjoyable to ride. If you find the right feed and routine you don’t need supplements. Ps his routine includes being bought in every night to reduce grass intake which played a big part in his behaviour!

We avoid anything with added magnesium as we found it had an adverse affect on our dressage horse. Analysis of normal feed plus mag supplement showed potential overdosing and the mare became fractious and struggled to respond effectively to riding aids.

I did use magnesium calmers, but after a couple of years, came to my senses. My horses were not behaving any better, and they were adding considerably to my feed costs. What actually worked was more turnout, and a mainly hay diet combined with high fibre, very low calorie feed. Perhaps in this age of horses spending all winter trapped inside stables, and riders afraid to hack, people are trying supplements to modify behaviour induced by the stresses of unnatural modern horse husbandry. When really, we need to be honest and accept that the horse was not designed to be kept that way, and change the way we care for them. Very few I would say need any more than a high fibre mash or cube and hay.

I always used to feed a little magnesium every day as I found it did calm my horse in the Spring and Autumn when the grass was putting on growth. I have heard too that it does help against laminitis. Perhaps you could advise on this please? Is there any evidence/research to confirm this ?
I moved to Wales where the grass is very, very lush and although my horse is not ridden now I keep on with a tiny scoop of magnesium every day.

Our land is very sandy based being close to the beach (yes we have amazing riding!) however my normally sane horse became increasingly silly over winter. High alert , spooky and wouldn’t allow you to touch him . It was like his brain had gone into over drive. No change in diet or routine. I started him on magnesium and he’s back to normal. It’s unlikely I’ll feed it all year round but I do believe there was some sort of deficiency causing his abnormal behaviour.